This invention relates to a novel optically active enone derivative, which is a useful intermediate for natural products such as prostagrandins and drugs, processes for the preparation thereof and a novel optically active compound as intermediates.
Recently, chiral alcohols with a plurality of hydroxyl groups have found wide and versatile utility as both enantiomers in the synthesis of optically active natural products or drugs and have become a focus of interest. In particular, the hydroxyl-protected enone form, i.e., 7,7-dimethyl-6,8-dioxabicyclo[3,3,0]oct-3-en-2-one, has been used as important building blocks for the synthesis of a variety of physiologically active substances such as prostagrandins.
Johnson et al. have accomplished a total synthesis of prostagrandin E2 from optically active 7,7-dimethyl-6,8-dioxabicyclo[3,3,0]oct-3-en-2-one (J. Am. Chem. Soc., 1986, 108, 5655). According to this process, the optically active enone was synthesized by optical resolution of the racemate with (+)-N,S-dimethyl-S-phenylsulfoximine. However, imine as a resolving agent is expensive, and the resolution according to the process should be made after addition of imine by conducting the reaction at a low temperature of xe2x88x9278xc2x0 C. Moreover, the process requires a reaction to regenerate a carbonyl group after resolution, which cannot always be easily carried out in an industrial scale. Thus, there has been a demand for a more simplified and convenient process for the preparation of an optically active enone, such as 7,7-dimethyl-6,8-dioxabicyclo[3,3,0]oct-3-en-2-one.
An object of the invention is to provide a more simplified process for the preparation of an optically active enone, such as 7,7-dimethyl-6,8-dioxabicyclo[3,3,0]-oct-3-en-2-one.
Another object of the invention is to provide intermediates obtainable during the process according to the invention.
Further object of the invention is to provide a novel optically active enone.
We have found a simplified and efficient process for the preparation of both enantiomers of an optically active enone, for example, 7,7-dimethyl-6,8-dioxabicyclo[3,3,0]oct-3-ene-2-one, starting an optically active alcohol derivative represented by the formula (9). 
wherein R1, R4 and R5 are as defined below.
Moreover, we have found that the intermediate obtained in the said process is a novel optically active compound, which is also useful chiral building blocks like the end product, i.e., optically active enone. The invention has been completed upon the above findings.
More specifically, as illustrated in Scheme 1 below, the present invention provides a process for the preparation of an optically active enone represented by the formula (4), which comprises steps of (A) deprotecting the protecting group for the hydroxyl group at the 1-position in a compound represented by the formula (1) to a hydroxyl group (compound (2)), (B) oxidizing the hydroxyl group to a ketone group (compound (3)) and (C) deprotecting the protecting group for the hydroxyl group at the 4-position to form a double bond between the carbon atom at the 4-position and the carbon atom at the 5-position to prepare the desired enone. Here all chemical names are referred to in accordance with the IUPAC nomenclature. For convenience sake, however, the position of a functional group shall be represented in accordance with the numbering as shown in the formula (1). 
wherein R1 and R4 independently represent a cumyl group, xcex1,xcex1-diethylbenzyl, xcex1,xcex1-dimethyl-p-methoxybenzyl, t-butyldimethylsilyl, trimethylsilyl, triethylsilyl, triisopropylsilyl, isopropyldimethylsilyl or ethyldimethylsilyl, R2 and R3 jointly represent acetonide, methyl ethyl ketal or diethyl ketal, and R5 represents a hydrogen atom, an alkyl group having not more than 20 carbon atoms or a phenyl group.
Also, as illustrated in Scheme 2 below, the invention provides a process for the preparation of an optically active enone represented by the formula (7), which comprises the steps of (Axe2x80x2) deprotecting the protecting group for the hydroxyl group at the 4-position in a compound represented by the formula (1) to a hydroxyl group (compound (5)), (Bxe2x80x2) oxidizing the hydroxyl group to a ketone group (compound (6)) and (Cxe2x80x2) deprotecting the protecting group for the hydroxyl group at the 1-position to form a double bond between the carbon atom at the 1-position and the carbon atom at the 5-position to prepare the desired enone. 
wherein R1, R2, R3, R4 and R5 are as defined above.
Further, as illustrated in Scheme 3 below, the invention provides a process for the preparation of an optically active enone represented by the formula (13), which comprises the steps of deprotecting the protecting group for the hydroxyl group at the 1-position in a compound represented by the formula (10) wherein the protecting group at the 1-position is a cumyl group and the protecting groups at the 2- and 3-positions are acetonide to a hydroxyl group (compound (11)); oxidizing the hydroxyl group to a ketone group (compound (12)); and deprotecting the protecting group for the hydroxyl group at the 4-position to form a double bond between the carbon atom at the 4-position and the carbon atom at the 5-position to prepare the desired enone. 
wherein R4 and R5 are as defined above.
Further, as illustrated in Scheme 4 below, the invention provides a process for the preparation of an optically active enone represented by the formula (16), which comprises the steps of deprotecting the protecting group for the hydroxyl group at the 4-position in a compound represented by the formula (10) wherein the protecting group at the 1-position is a cumyl group and the protecting groups at the 2- and 3-positions are acetonide to a hydroxyl group (compound (14)); oxidizing the hydroxyl group to a ketone group (compound (15)); and deprotecting the protecting group for the hydroxyl group at the 1-position to form a double bond between the carbon atom at the 1-position and the carbon atom at the 5-position to prepare the desired enone. 
wherein R4 and R5 are as defined above.
Moreover, as illustrated in Scheme 5 below, the invention provides a process for the preparation of an optically active enone represented by the formula (16), which comprises the steps of deprotecting the protecting group for the hydroxyl group at the 4-position in a compound represented by the formula (17) wherein the protecting group at the 4-position is a cumyl group and the protecting groups at the 2- and 3-positions are acetonide to a hydroxyl group (compound (18)); oxidizing the hydroxyl group to a ketone group (compound (19)); and deprotecting the protecting group for the hydroxyl group at the 1-position to form a double bond between the carbon atom at the 1-position and the carbon atom at the 5-position to prepare the desired enone. 
wherein R1 and R5 are as defined above.
Also, as illustrated in Scheme 6 below, the invention provides a process for the preparation of an optically active enone represented by the formula (13), which comprises the steps of deprotecting the protecting group for the hydroxyl group at the 1-position in a compound represented by the formula (17) wherein the protecting group at the 4-position is a cumyl group and the protecting groups at the 2- and 3-positions are acetonide to a hydroxyl group (compound (20)); oxidizing the hydroxyl group to a ketone group (compound (21)); and deprotecting the protecting group for the hydroxyl group at the 4-position to form a double bond between the carbon atom at the 4-position and the carbon atom at the 5-position to prepare the desired enone. 
wherein R1 and R5 are as defined above.
Still further, the invention provides an optically active compound represented by the formula (1). The compounds represented by the formula (1) include enantiomers thereof.
The invention also provides optically active compounds represented by the formulae (2)-(7), (9)-(21) and (23)-(25) as illustrated in the below-mentioned Schemes.
The present invention will be explained below in more detail.
The process for the preparation of an optically active enone according to this invention comprises the step A or Axe2x80x2 wherein the protecting group at the 1-position or the 4-position in a compound represented by the formula (1) is deprotected, the step B or Bxe2x80x2 wherein the deprotected hydroxyl group is oxidized to a ketone group, and the step C or step Cxe2x80x2 wherein the protecting group at the 4-position or the 1-position is deprotected followed by dehydration to form a double bond, as illustrated by the following Scheme 7. In this case, it may be feasible to selectively synthesize any enantiomer by first deprotecting either of the hydroxyl groups. 
More specifically, the upper route in Scheme 7 comprising the steps A, B and C, wherein the protecting group at the 1-position in the compound (1) is first deprotected, can selectively produce the optically active enone represented by the formula (4), whereas the lower route comprising the step Axe2x80x2, Bxe2x80x2 and Cxe2x80x2, wherein the protecting group at the 4-position in the compound (1) is first deprotected, can selectively produce an enantiomer of the optically active enone represented by the formula (4), as shown by the formula (7). When the protecting groups R2 and R3 form acetonide and the protecting group R5 is a hydrogen atom, the dextro-rotatory compound represented by the formula (37), (+)-7,7-dimethyl-6,8-dioxabicyclo[3,3,0]-oct-3-en-2-one, is obtained according to the upper route in Scheme 7. On the other hand, the levo-rotatory compound represented by the formula (40), (xe2x88x92)-7,7-dimethyl-6,8-dioxabicyclo[3,3,0]oct-3-en-2-one, is obtained according to the lower route.
As already mentioned, the compounds represented by the formula (1) may include enantiomers thereof. Thus, all optically active compounds prepared using the compound of the formula (1) as a starting material may also include enantiomers thereof. In short, when the enantiomer of the compound represented by the formula (1) is used as a starting material, whose protecting groups R2 and R3 form acetonide and protecting group R5 is a hydrogen atom, the levo-rotatory compound represented by the formula (40), (xe2x88x92)-7,7-dimethyl-6,8-dioxabicyclo[3,3,0]-oct-3-en-2-one, is obtained according to the upper route in Scheme 7. On the other hand, the dextro-rotatory compound represented by the formula (37), (+)-7,7-dimethyl-6,8-dioxabicyclo[3,3,0]oct-3-en-2-one, is obtained according to the lower route.
In other words, any enantiomer may be selectively synthesized depending on the chirality of the starting optically active compound and the hydroxyl group to be first deprotected.
The optically active enone, which may be prepared according to the process of this invention, is the compounds represented by the formulae (4) and (7), respectively, wherein R2, R3 and R4 are within the scope mentioned below.
The protecting groups R2 and R3 for a hydroxyl group in the invention may be any of those groups that may act as a protecting group for a hydroxyl group and could not be eliminated by the deprotection reaction for the protecting group R1 or R4. The protecting groups R2 and R3 may be independent each other, and they may be joined together with the carbon atoms at the 2-position and the 3-position in the cyclopentane ring to form a ring.
Preferably, the protecting groups R2 and R3 are joined together, such as methyl ethyl ketal, diethyl ketal and acetonide, acetonide being more preferable.
The group R5 in the present invention is any of those functional groups that do not inhibit the reactions according to the invention. Preferably, it may be a hydrogen atom, an alkyl group or a phenyl group. A hydrogen atom and an alkyl group of 20 or less carbon atoms are particularly preferred.
The compound represented by the formula (1), which is a starting material in the process for the preparation of an optically active enone according to the invention, has the following characteristics. R2, R3 and R5 in the formula (1) are within the same scope as defined above.
The protecting groups R1 and R4 for a hydroxyl group in the invention may be any of those groups that may act as a protecting group for a hydroxyl group. Preferably, there may be mentioned ether-type protecting groups, silyl ether-type protecting groups and ester-type protecting groups. The ether-type protecting groups may include, for example, methoxymethyl, t-butylthiomethyl, t-butoxymethyl, siloxymethyl, 2,2,2-trichloroethoxymethyl, 2-(trimethylsilyl)ethoxymethyl, tetrahydropyranyl, tetrahydrofuranyl, 1-ethoxyethyl, 1-methyl-1-methoxyethyl, 2,2,2-trichloroethyl, 2-trimethylsilylethyl, t-butyl, allyl, benzyl, p-methoxybenzyl, nitrobenzyl, cumyl group, xcex1,xcex1-diethylbenzyl, xcex1-methyl-xcex1-ethylbenzyl and xcex1,xcex1-dimethyl-p-methoxybenzyl. The silyl ether-type protecting groups may include, for example, trimethylsilyl, triethylsilyl, triisopropylsilyl, isopropyldimethylsilyl, ethyldimethylsilyl, and t-butyldimethylsilyl. The ester-type protecting groups may include, for example, acetyl, chloroacetyl, dichloroacetyl, trichloroacetyl, trifluoroacetyl, methoxyacetyl, pivaloyl or benzoyl. Of these groups, the ether-type and silyl ether-type protecting groups are preferable and cumyl group, xcex1,xcex1-diethylbenzyl, xcex1,xcex1-dimethyl-p-methoxybenzyl or t-butyldimethylsilyl is more preferable.
The protecting group R1 in the present invention is not deprotected by the deprotection reaction for the protecting groups R4 and is deprotected selectively by the deprotection reaction for R1, and the protecting group R4 is not deprotected by the deprotection reaction for the protecting group R1 and is deprotected selectively by the deprotection reaction for R4.
For instance, the ether-type protecting group may be deprotected by hydrogenolysis, the silyl ether-type protecting group may be deprotected by alcoholysis under basic condition, and the ester-type protecting group may be deprotected under condition of potassium carbonate-alcohol. When R2 and R3 form acetonide, which may be deprotected under acidic condition, the above parameters may be satisfied by selecting R1 and R4 from the above-mentioned ether-type, silyl ether-type and ester-type protecting groups.
Illustrative are the following Schemes 8-11: 
In these Schemes, R5 is as defined above.
Synthesis of the compounds represented by the formulae (26) and (27), which may be used as a starting material, is illustrated by the following Schemes 12 and 13, respectively. 
In these Schemes, R5 is as defined above.
According to the upper route in the aforementioned Scheme 7, the optically active enone represented by the formula (4) may be prepared starting from the compound represented by the formula (1) through the step A, the step B and the step C. Each of these steps will be explained later.
Process for the preparation of the compound (1) in Scheme 7
As illustrated in Scheme 14 below, the optically active compound (1) is prepared starting from a cyclopentene derivative (8), via a cyclopentanediol derivative (9) and subsequent protection of the diol. 
The reaction for preparing the cyclopentanediol derivative (9) from the cyclopenetene derivative (8) (wherein R1, R4 and R5 are as defined above) may be carried out using any well-known oxidation reaction for cis-addition, and manganese oxidation and osmium oxidation are preferable. Osmium oxidation is particularly preferable.
The compound represented by the formula (8) may be prepared by reacting cyclopentadiene with cumene peroxide and Cu(OAc)2, converting OAc to OH according to our method (Synthesis, 2000, 6, 817), oxidizing a hydroxyl group to a ketone group using as a catalyst manganese oxide in a mixed solvent of dichloromethane/hexane (1/5), reducing the ketone with NaBH4 and finally protecting a hydroxyl group with another protecting group. The cumyl group may be deprotected and then replaced with another protecting group.
As illustrated in Schemes 15 and 16, the compound (10) or (17) may be prepared, for example, by osmium oxidation of the cyclopentene derivative (8) wherein R1 is a cumyl group (compound (22)) or the cyclopentene derivative (8) wherein R4 is a cumyl group (compound (24)), to form the 2,3-diol compound represented by the formula (23) or (25) and protecting hydroxyl groups with acetonide by reacting the diol compound with acetal dimethyl ketal. 
wherein R1 and R5 are as defined above.
Specifically, the cyclopentadiene derivatives represented by the formula (8) wherein R1 is a cumyl group and R5 is a hydrogen atom, i.e., (+)-cis-4-cumyloxy-2-cyclopenten-1-ol derivative, may be prepared according to the method disclosed in our report (Synlett 1999, 11, 1754-1756).
More specifically, racemic cis-4-cumyloxy-2-cyclopenten-1-ol is first prepared from dicyclopentadiene. Then, the racemate is transesterified or esterified by treating with a carboxylic acid ester or a carboxylic acid in the presence of a hydrolase to prepare (+)-cis-4-cumyloxy-2-cyclopenten-1-ol. Thereafter, the hydroxyl group is again protected with other protecting group R4 than a cumyl group to prepare (+)-cis-4-cumyloxy-2-cyclopenten-1-ol derivative represented by the formula (22).
The compound (22) thus prepared is then subjected to osmium oxidation to form the diol compound (23) and then the hydroxyl groups are protected with acetonide to prepare the compound (10).
The Steps A, B and C are illustrated below.
1) Step A
The step A is the step wherein the protecting group at the 1-position of the optically active compound (1) is deprotected to prepare the optically active compound (2). Any well-known deprotection reaction may be applied provided that only the protecting group at the 1-position can be deprotected without deprotecting the protecting group at the 4-position. A preferable deprotection reaction may depend on combination of the 1-protecting group with the 4-protecting group. For instance, a catalytic reduction reaction using a palladium-carbon catalyst under hydrogen atmosphere is preferable when the protecting group at the 1-position is a cumyl group and the protecting group at the 4-position is a t-butyldimethylsilyl group.
Those skilled in the art could easily select the optimum protecting group in accordance with, for example, Theodora W. Green, Peter G. M. Wuts, xe2x80x9cProtecting groups in Organic Synthesisxe2x80x9d, Third Ed., Wiley-Interscience. Also, it will be easy for those skilled in the art to optimize reaction conditions, for example, solvents or reaction temperatures.
The compound represented by the formula (2) prepared in the step A, may be isolated by any well-known isolation method. The compound may be isolated and purified, for example, by extraction or liquid chromatography. The isolated compound (2) may be identified by any well-known analytical method. The molecular structure thereof may be determined, for example, by determining spectra such as mass spectra, infrared absorption spectra or nuclear magnetic resonance spectra as well as elementary analysis. Those skilled in the art may easily isolate and purify the compound (2) as prepared in the step A and then identify the isolated compound according to any well-known method.
The compound (2) as prepared and isolated according to the process of the invention has a high purity and a high optical purity.
2) Step B
The step B is the step wherein the hydroxyl group in the optically active compound (2) as prepared in the step A is oxidized to a ketone group to prepare the optically active compound (3). Any well-known oxidation reaction may be applied provided that it may oxidize the hydroxyl group of the compound (2) to a ketone group. Preferably, the oxidation reaction is carried out without damaging the protecting groups R2, R3 and R4.
The oxidizing agent used in the step for oxidizing the hydroxyl group in the compound (2) to a ketone group to prepare the compound (3) is not restricted provided that it can oxidize only the hydroxyl group without damaging the protecting groups R2, R3 and R4. Preferable are heavy metal-type oxidizing agents or organic compound-type oxidizing agents. Heavy metal-type oxidizing agents may include, for example, potassium permanganate, manganese dioxide, chromium oxide-pyridine complex, pyridinium chlorochromate, pyridinium dichromate, lead acetate or silver carbonate. Organic compound-type oxidizing agents may include, for example, m-chloroperbenzoic acid, dimethyl sulfoxide/oxalyl chloride or Dess-Martin reagent. Organic compound-type oxidizing agents are particularly preferable, with Dess-Martin reagent being more preferable.
The compound represented by the formula (3) prepared in the step B may be isolated by any well-known isolation method, for example, by extraction or liquid chromatography. The isolated compound (3) may be identified by any well-known analytical method. The molecular structure thereof may be determined, for example, by determining spectra such as mass spectra, infrared absorption spectra or nuclear magnetic resonance spectra as well as elementary analysis. Those skilled in the art may easily isolate and purify, and identify the compound (3) according to any known methods.
The compound (3) prepared and isolated according to the present process has a high purity and a high optical purity.
3) Step C
The step C is the step wherein the protecting group at the 4-position of the compound (3) as prepared in the step B is deprotected to form a double bond between the carbon atom at the 4-position and the carbon atom at the 5-position, whereby the optically active compound (4) is prepared. Any well-known reaction may be applied provided that it may deprotect the protecting group R4 at the 4-position of the compound (3) to form a double bond between the carbon atom at the 1-position and the carbon atom at the 4-position. Preferably, the reaction is one wherein R4 is deprotected without any damage to the protecting groups R2 and R3 to form a double bond between the carbon atom at the 4-position and the carbon atom at the 5-position. For instance, when the protecting groups R2 and R3 form acetonide and the protecting group R4 at the 4-position is a t-butyldimethylsilyl group, it is preferable that the t-butyldimethylsilyl group is deprotected by a reaction in acetic acid at 60xc2x0 C. and a double bond is formed between the carbon atoms at the 4-position and the 5-position by dehydration reaction.
Those skilled in the art may easily select the optimum reaction from well-known reactions.
The compound represented by the formula (4) prepared in the step C may be isolated by any well-known isolation method, for example, by extraction or liquid chromatography. The isolated compound (4) may be identified by any well-known analytical method. The molecular structure thereof may be determined, for example, by determining spectra such as mass spectra, infrared absorption spectra or nuclear magnetic resonance spectra as well as elementary analysis. Those skilled in the art may easily isolate and purify, and identify the compound (4) according to any known methods.
When the compound represented by the formula (4) is a known compound, the compound may also be identified by comparing the measurements obtained with those as referred to in literatures.
The compound (4) prepared and isolated according to the present process has a high purity and a high optical purity.
According to the lower route in the aforementioned Scheme 7, the optically active enone represented by the formula (7) may be prepared starting from the compound represented by the formula (1) through the step Axe2x80x2, the step Bxe2x80x2 and the step Cxe2x80x2. Each of these steps will be explained below.
1) Step Axe2x80x2
The step Axe2x80x2 is the step wherein the protecting group at the 4-position of the optically active compound (1) is deprotected to prepare the optically active compound (5). Any well-known deprotection reaction may be applied provided that only the protecting group at the 4-position can be deprotected without deprotecting the protecting group at the 1-position. A preferable deprotection reaction may depend on combination of the 1-protecting group with the 4-protecting group. For instance, the deprotection reaction using tetrabutylammonium fluoride in a solvent is preferable, when the protecting group at the 1-position R1 is a cumyl group and the protecting group at the 4-position R4 is a t-butyldimethylsilyl group.
The compound represented by the formula (5) prepared in the step Axe2x80x2 may be isolated by any well-known isolation method. The compound may be isolated and purified, for example, by extraction or liquid chromatography. The isolated compound (5) may be identified by any well-known analytical method. The molecular structure thereof may be determined, for example, by determining spectra such as mass spectra, infrared absorption spectra or nuclear magnetic resonance spectra as well as elementary analysis. Those skilled in the art may easily isolate and purify the compound (5) as prepared in the step Axe2x80x2 and then identify the isolated compound according to any well-known method.
The compound (5) as prepared and isolated according to the process of the invention has a high purity and a high optical purity.
2) Step Bxe2x80x2
The step Bxe2x80x2 is the step wherein the hydroxyl group in the optically active compound (5) as prepared in the step Axe2x80x2 is oxidized to a ketone group to prepare the optically active compound (6). Any well-known oxidation reaction may be applied provided that it may oxidize the hydroxyl group of the compound (5) to a ketone group. Preferably, the oxidation reaction is carried out without damaging the protecting groups R1, R2 and R3.
The oxidizing agent used in the step for oxidizing the hydroxyl group in the compound (5) to a ketone group to prepare the compound (6) is not restricted provided that it can oxidize only the hydroxyl group without damaging the protecting groups R1, R2 and R3. Preferable are heavy metal-type oxidizing agents or organic compound-type oxidizing agents. Heavy metal-type oxidizing agents may include, for example, potassium permanganate, manganese dioxide, chromium oxide-pyridine complex, pyridinium chlorochromate, pyridinium dichromate, lead acetate or silver carbonate. Organic compound-type oxidizing agents may include, for example, m-chloroperbenzoic acid, dimethyl sulfoxide/oxalyl chloride or Dess-Martin reagent. Organic compound-type oxidizing agents are particularly preferable, with Dess-Martin reagent being more preferable.
The compound represented by the formula (6) prepared in the step Bxe2x80x2 may be isolated by any well-known isolation method, for example, by extraction or liquid chromatography. The isolated compound (6) may be identified by any well-known analytical method. The molecular structure thereof may be determined, for example, by determining spectra such as mass spectra, infrared absorption spectra or nuclear magnetic resonance spectra as well as elementary analysis. Those skilled in the art may easily isolate and purify, and identify the compound (6) according to any known methods.
The compound (6) prepared and isolated according to the present process has a high purity and a high optical purity.
3) Step Cxe2x80x2
The step Cxe2x80x2 is the step wherein the protecting group at the 1-position of the compound (6) as prepared in the step Bxe2x80x2 is deprotected to form a double bond between the carbon atom at the 1-position and the carbon atom at the 5-position, whereby the optically active compound (7) is prepared. Any well-known reaction may be applied provided that it may deprotect the protecting group R1 at the 1-position of the compound (6) to form a double bond between the carbon atom at the 1-position and the carbon atom at the 5-position. Preferably, the reaction is one wherein R1 is deprotected without any damage to the protecting groups R2 and R3 to form a double bond between the carbon atom at the 1-position and the carbon atom at the 5-position. For instance, when the protecting groups R2 and R3 form acetonide and the protecting group R1 at the 1-position is a cumyl group, it is preferable that the cumyl group is deprotected by a reaction in acetic acid at 60xc2x0 C. and a double bond is formed between the carbon atoms at the 1-position and the 5-position by dehydration reaction.
Those skilled in the art may easily select the optimum reaction from well-known reactions.
The compound represented by the formula (7) prepared in the step Cxe2x80x2 may be isolated by any well-known isolation method, for example, by extraction or liquid chromatography. The isolated compound (7) may be identified by any well-known analytical method. The molecular structure thereof may be determined, for example, by determining spectra such as mass spectra, infrared absorption spectra or nuclear magnetic resonance spectra as well as elementary analysis. Those skilled in the art may easily isolate and purify, and identify the compound (7) according to any known methods.
When the compound represented by the formula (7) is a known compound, the compound may also be identified by comparing the measurements obtained with those as referred to in literatures.
The compound (7) prepared and isolated according to the present process has a high purity and a high optical purity.
The invention will be illustrated in greater detail by way of the following Examples, but the invention is not to be limited thereto. And, the reactions for the optically active enones as obtained by the following examples are as shown in the following Schemes 17-22. 